Arizona Geological Society: From Taxpayer Liability to a Top 10 US Copper Producer

The Cactus Project is comprised of three deposits and one Stockpile within a 5.5 km mine trend, including the past producing Sacaton Mine, the deposits now known as Cactus East and Cactus West, in addition to the Parks/Salyer deposit, SW along the mine trend.

The Cactus and Parks/Salyer deposits are portions of a large porphyry copper system that has been dismembered and displaced by Tertiary extensional faulting. Porphyry copper deposits form in areas of shallow magmatism within subduction-related tectonic environments (Berger et al., 2008).

GEOLOGY & DEPOSIT.  Major host rocks are Precambrian Oracle Granite and Laramide monzonite porphyry and quartz monzonite porphyry. The porphyries intruded the older rocks to form mixed breccias; monolithic breccias and occur as large masses, poorly defined dike-like masses; and thin well-defined but discontinuous dikes.  The deposit is structurally complex with intense fracturing, faulting, and both pre-mineral and post-mineral brecciation. It is bounded on the east and west sides by normal faults.

Chalcocite and covellite are the only supergene sulfides recognized. The chalcocite blanket in the mineralized zone is irregular in thickness, grade, and continuity. The thickness of leached capping varies from less than 100 ft (30 m) to over 650 ft (198 m), with the thicker intercepts on the north side. Substantial quantities of oxidized copper minerals are found erratically distributed through the capping. Chrysocolla, brochantite, and malachite are the most common oxidized copper minerals. In upper portions of the capping, chrysocolla predominates, while brochantite and malachite predominate in the lower portions.

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